The present invention relates generally to semiconductor devices, and more particularly to the formation of III-V semiconductor devices with starting layers which can be selectively oxidized.
The fabrication of semiconductor devices involves forming electronic components in and on semiconductor substrates, such as silicon wafers. These electronic components may include one or more conductive layers, one or more insulation layers, and doped regions formed by implanting various dopants into portions of a semiconductor substrate to achieve specific electrical properties. Semiconductor devices include transistors, resistors, capacitors, and the like, with intermediate and overlying metallization patterns at varying levels, separated by dielectric materials, which interconnect the semiconductor devices to form integrated circuits.
To electrically isolate semiconductor devices from each other, various isolation techniques, such as trench isolation structures, have been used. Viewing the vertical direction as into the depth, or thickness, of a given substrate and the horizontal direction as being parallel to a top surface of the substrate, a trench isolation structure is vertically oriented to provide insulating separation between semiconductor devices at different horizontal locations. Traditionally, a semiconductor surface is etched to form separate device regions, and resulting trenches in between the separate device regions are filled with dielectric material to form the trench isolation structures.
A semiconductor substrate may also employ semiconductor-on-insulator substrate arrangements, such as silicon-on-insulator (SOI) substrates. In a semiconductor on insulator arrangement, a semiconductor layer can be formed above an insulation layer which has been formed on the semiconductor substrate. Devices can be formed in the top semiconductor layer. The insulating layer provides isolation from the substrate, thereby decreasing capacitance effects for both devices and electrical connections. The top semiconductor layer can be etched, as described above, to provide trench isolation between device regions.
Growing an epitaxial insulating layer on a semiconductor substrate is known. Oxides such as strontium titanium oxides (e.g., SrTiO3) and yttrium oxides (e.g., Y2O3) have been grown on silicon substrates. More recently, epitaxial structures with closer lattice-matching have been grown, allowing for silicon substrate/epitaxial oxide/epitaxial silicon multi-layer structures. Grown epitaxial oxides with closer lattice-matching properties include oxides of rare earth metals and rare earth metal alloys, such as cerium, yttrium, lanthanum, samarium, gadolinium, europium, and combinations thereof (e.g., cerium oxides (CeO2) and lanthanum yttrium oxides (LaxY1-x)2O3).